Color television tube with shadow mask provided with electron shielding plate coated with heat radiating material



Oct. 24, 1967 R. R. BATHELT ET AL 3,349,272

COLOR TELEVISION TUBE WITH SHADOW MASK PROVIDED WITH ELECTRON SHIELDING PLATEYCOATED WITH HEAT RADIATING MATERIAL Filed Nov. 14, 1966 ggnsmma wm 2;, e r. AGEN United States Patent 3,349,272 COLOR TELEVISION TUBE WITH SHADOW MASK PROVIDED WITH ELECTRON SHIELDING PLATE COATED WITH HEAT RADIATING MA- TERIAL Robert Richard Bathelt, Emmasingel, Eindhoven, Jan Care] Francken, Groningen, and Constantins Johannes Walthems Panis, Emmasingel, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Nov. 14, 1966, Ser. No. 594,242 Claims priority, application Netherlands, Dec. 16, 1965, 656,386 3 Claims. (Cl. 313-85) ABSTRACT OF THE DISCLOSURE An annular protective plate secured with minimum heat conductivity to a frame which supports a color-selection member in a cathode-ray tube for color television reproduction.

The invention relates to a cathode-ray tube for displaying color television images. More particularly, the invention relates to a screen plate which protects a frame of ferromagnetic material to which a color selection member in proximity to the display screen is secured.

An annular screen plate secured to the wall of the tube has been provided, on the cathode side of a color selection electrode and a color selection electrode suspended so that temperature variations result in radial displacements of the apertures of the color selection electrode. However, this construction is complicated and hence expensive.

According to the present invention, an inexpensive solution is obtained because the screen plate is solely supported by the frame of the color selection electrode. In addition steps have been taken to reduce the heat transfer from the screen plate to the frame.

The screen plate is heated by the electrons which upon deflection would get outside the image surface and which otherwise would impinge on the frame of the color selection electrode. Since this electrode is generally suspended in the envelope by means of a few thin leaf springs, it cannot transmit heat to the bulb by conduction. The heat must therefore be transmitted entirely by radiation. For this purpose, the frame and preferably also the whole color selection electrode are blackened. Because the frame is now no longer heated by primary electrons, the quantity of heat irradiated by it is considerably smaller so that the frame remains much cooler. Therefore, heating of the frame must be prevented by heat conduction from the annular screen and this is achieved by a poorly heat-conducting joint by means of which the screen is secured to the frame. Furthermore, the surface of the annular screen facing the cathode is blackened, whereas the side facing the frame is left uncovered.

The invention will now be described more fully with reference to the accompanying drawing, in which FIG. 1 is a longitudinal sectional view of a cathode-ray tube in accordance with the invention, and

FIGS. 2 and 3 show embodiments in accordance with the invention of methods of securing an annular screen to the supporting frame of the color selection member.

Referring now to FIG. 1, reference numeral 1 designates the glass envelope of a cathode-ray tube the window 2 of which is coated on the inner side with a phosphor screen 3 consisting of phosphor dots luminescing in various colors. In the proximity of this phosphor screen 3, there is provided on the side facing an electron gun (not shown) a color selection elecetrode 4 in the form of an apertured shadow-mask plate which is secured on a frame 5 suspended in the envelope 1 by means of a plurality of thin leaf springs (no-t shown). The maximum deflection at which the electrons of the beam 6 (consisting in this case of three rays) still strike the phosphor screen is indicated in FIG. 1. With a view to deviations in the deflec tion circuit arrangements, however, the deflection is generally effected through a larger angle, as is shown with the rays 7. The electrons impinge on the annular plate 8. This plate 8 is secured on the supporting frame 5 so that the heat transfer from the plate 8 to the frame 5 is low. For this purpose, the annular plate 8 may be secured to the frame 5 by means of a few narrow strips 9, 10 bent into the shape of a U, as shown in FIG. 2, or the plate 8 may be locally provided with depressions 11 the summits of which may be welded to the frame 5.

The frame 5, the shadow mask 4 and the plate 8 may be made of inexpensive material such as iron, since the frame 5 does not become excessively hot, while the plate 8 can expand substantially freely, since the joint obtained by the strips 9, 10 or the depressions 11 has a sufiicient elasticity to absorb expansion differences between the cooler frame 5 and the hotter annular plate 8. The surface of the annular plate 8 facing the electron gun is coated with a black layer (for example, of chromium oxide or of an aluminum-iron compound), just like the outer surface of the frame 5 and, if desired, of the strips 9. The mask 4 is also blackened, preferably on both sides.

While the invention has been described with reference to particular embodiments and applications thereof, other modifications will be apparent to those skilled in the art without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. A cathode-ray tube for displaying color television images comprising an envelope, a fluorescent display screen supported by a portion of the inner wall of said envelope, a color selection member in proximity to said display screen, a frame consisting of ferromagnetic material to which said color selection member is secured, an annular plate on the side of said color selection member remote from said display screen which protects the frame from being struck by an electron beam, and means to secure said annular plate to the frame with reduced heat transfer from the annular plate to the frame.

2. A cathode-ray tube as claimed in claim 1, in which the surface of the annular plate remote from the frame is blackened, whereas the surface facing the frame is uncovered.

3. A cathode-ray tube as claimed in claim 2, in which the frame and the annular plate consist of iron.

References Cited UNITED STATES PATENTS 2,054,119 9/1936 Daene 313--40 2,832,911 4/1958 Van Velzer 313-78 2,890,377 6/1959 Fyler 313- X DAVID J. GALVIN, Primary Examiner.

V. LAFRANCHI, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,349,272 October 24, 1967 Robert Richard Bathelt et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, line 13, for "65-6 ,386" read 6516386 Signed and sealed this 3rd day of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A CATHODE-RAY TUBE FOR DISPLAYING COLOR TELEVISION IMAGES COMPRISING AN ENVELOPE, A FLUORESCENT DISPLAY SCREEN SUPPORTED BY A PORTION OF THE INNER WALL OF SAID ENVELOPE, A COLAR SELECTION MEMBER IN PROXIMITY TO SAID DISPLAY SCREEN, A FRAME CONSISTING OF FERROMAGNETIC MATERIAL TO WHICH SAID COLOR SELECTION MEMBER IS SECURED, AN ANNULAR PLATE ON THE SIDE OF COLOR SELECTION MEMBER REMOTE FROM SAID DISPLAY SCREEN WHICH PROTECTS THE FRAME FROM BEING STRUCK BY AN ELECTRON BEAM, AND MEANS TO SECURE SAID ANNULAR PLATE TO THE FRAME WITH REDUCED HEAT TRANSFER FROM THE ANNULAR PLATE TO THE FRAME. 